HADOOP-8814. Replace string equals by String#isEmpty(). Contributed by Brandon Li.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1387853 13f79535-47bb-0310-9956-ffa450edef68

hadoop-common-project/hadoop-common/CHANGES.txt

@@ -103,6 +103,9 @@ Trunk (Unreleased)
 
     HADOOP-8736. Add Builder for building RPC server. (Brandon Li via Suresh)
 
+    HADOOP-8814. Replace string equals "" by String#isEmpty().
+    (Brandon Li via suresh)
+
   BUG FIXES
 
     HADOOP-8177. MBeans shouldn't try to register when it fails to create MBeanName.

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/conf/Configuration.java

@@ -1073,7 +1073,7 @@ public class Configuration implements Iterable<Map.Entry<String,String>>,
    */
   public boolean getBoolean(String name, boolean defaultValue) {
     String valueString = getTrimmed(name);
-    if (null == valueString || "".equals(valueString)) {
+    if (null == valueString || valueString.isEmpty()) {
       return defaultValue;
     }
 
@@ -1140,7 +1140,7 @@ public class Configuration implements Iterable<Map.Entry<String,String>>,
    */
   public Pattern getPattern(String name, Pattern defaultValue) {
     String valString = get(name);
-    if (null == valString || "".equals(valString)) {
+    if (null == valString || valString.isEmpty()) {
       return defaultValue;
     }
     try {

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/conf/ReconfigurationServlet.java

@@ -153,9 +153,9 @@ public class ReconfigurationServlet extends HttpServlet {
           StringEscapeUtils.unescapeHtml(req.getParameter(rawParam));
         if (value != null) {
           if (value.equals(newConf.getRaw(param)) || value.equals("default") ||
-              value.equals("null") || value.equals("")) {
+              value.equals("null") || value.isEmpty()) {
             if ((value.equals("default") || value.equals("null") || 
-                 value.equals("")) && 
+                 value.isEmpty()) && 
                 oldConf.getRaw(param) != null) {
               out.println("<p>Changed \"" + 
                           StringEscapeUtils.escapeHtml(param) + "\" from \"" +
@@ -163,7 +163,7 @@ public class ReconfigurationServlet extends HttpServlet {
                           "\" to default</p>");
               reconf.reconfigureProperty(param, null);
             } else if (!value.equals("default") && !value.equals("null") &&
-                       !value.equals("") && 
+                       !value.isEmpty() && 
                        (oldConf.getRaw(param) == null || 
                         !oldConf.getRaw(param).equals(value))) {
               // change from default or value to different value

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/FileContext.java

@@ -2003,7 +2003,7 @@ public final class FileContext {
       String filename = inPathPattern.toUri().getPath();
       
       // path has only zero component
-      if ("".equals(filename) || Path.SEPARATOR.equals(filename)) {
+      if (filename.isEmpty() || Path.SEPARATOR.equals(filename)) {
         Path p = inPathPattern.makeQualified(uri, null);
         return getFileStatus(new Path[]{p});
       }

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/FileSystem.java

@@ -1597,7 +1597,7 @@ public abstract class FileSystem extends Configured implements Closeable {
     String filename = pathPattern.toUri().getPath();
     
     // path has only zero component
-    if ("".equals(filename) || Path.SEPARATOR.equals(filename)) {
+    if (filename.isEmpty() || Path.SEPARATOR.equals(filename)) {
       return getFileStatus(new Path[]{pathPattern});
     }
 

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/Path.java

@@ -68,7 +68,7 @@ public class Path implements Comparable {
     // Add a slash to parent's path so resolution is compatible with URI's
     URI parentUri = parent.uri;
     String parentPath = parentUri.getPath();
-    if (!(parentPath.equals("/") || parentPath.equals(""))) {
+    if (!(parentPath.equals("/") || parentPath.isEmpty())) {
       try {
         parentUri = new URI(parentUri.getScheme(), parentUri.getAuthority(),
                       parentUri.getPath()+"/", null, parentUri.getFragment());

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/RawLocalFileSystem.java

@@ -492,7 +492,7 @@ public class RawLocalFileSystem extends FileSystem {
      * onwer.equals("").
      */
     private boolean isPermissionLoaded() {
-      return !super.getOwner().equals(""); 
+      return !super.getOwner().isEmpty(); 
     }
     
     RawLocalFileStatus(File f, long defaultBlockSize, FileSystem fs) {

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/local/RawLocalFs.java

@@ -128,7 +128,7 @@ public class RawLocalFs extends DelegateToFileSystem {
     try {
       FileStatus fs = getFileStatus(f);
       // If f refers to a regular file or directory      
-      if ("".equals(target)) {
+      if (target.isEmpty()) {
         return fs;
       }
       // Otherwise f refers to a symlink
@@ -150,7 +150,7 @@ public class RawLocalFs extends DelegateToFileSystem {
        * the readBasicFileAttributes method in java.nio.file.attributes 
        * when available.
        */
-      if (!"".equals(target)) {
+      if (!target.isEmpty()) {
         return new FileStatus(0, false, 0, 0, 0, 0, FsPermission.getDefault(), 
             "", "", new Path(target), f);        
       }

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/s3native/NativeS3FileSystem.java

@@ -300,7 +300,7 @@ public class NativeS3FileSystem extends FileSystem {
   }
   
   private static String pathToKey(Path path) {
-    if (path.toUri().getScheme() != null && "".equals(path.toUri().getPath())) {
+    if (path.toUri().getScheme() != null && path.toUri().getPath().isEmpty()) {
       // allow uris without trailing slash after bucket to refer to root,
       // like s3n://mybucket
       return "";

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ha/ActiveStandbyElector.java

@@ -276,7 +276,7 @@ public class ActiveStandbyElector implements StatCallback, StringCallback {
 
     String pathParts[] = znodeWorkingDir.split("/");
     Preconditions.checkArgument(pathParts.length >= 1 &&
-        "".equals(pathParts[0]),
+        pathParts[0].isEmpty(),
         "Invalid path: %s", znodeWorkingDir);
     
     StringBuilder sb = new StringBuilder();

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ha/SshFenceByTcpPort.java

@@ -241,7 +241,7 @@ public class SshFenceByTcpPort extends Configured
       sshPort = DEFAULT_SSH_PORT;
 
       // Parse optional user and ssh port
-      if (arg != null && !"".equals(arg)) {
+      if (arg != null && !arg.isEmpty()) {
         Matcher m = USER_PORT_RE.matcher(arg);
         if (!m.matches()) {
           throw new BadFencingConfigurationException(

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/DefaultStringifier.java

@@ -192,7 +192,7 @@ public class DefaultStringifier<T> implements Stringifier<T> {
       String[] parts = itemStr.split(SEPARATOR);
 
       for (String part : parts) {
-        if (!part.equals(""))
+        if (!part.isEmpty())
           list.add(stringifier.fromString(part));
       }
 

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/file/tfile/TFile.java

@@ -2105,7 +2105,7 @@ public class TFile {
     }
 
     public boolean isSorted() {
-      return !strComparator.equals("");
+      return !strComparator.isEmpty();
     }
 
     public String getComparatorString() {

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics/util/MetricsDynamicMBeanBase.java

@@ -129,7 +129,7 @@ public abstract class MetricsDynamicMBeanBase implements DynamicMBean {
   @Override
   public Object getAttribute(String attributeName) throws AttributeNotFoundException,
       MBeanException, ReflectionException {
-    if (attributeName == null || attributeName.equals("")) 
+    if (attributeName == null || attributeName.isEmpty()) 
       throw new IllegalArgumentException();
     
     updateMbeanInfoIfMetricsListChanged();
@@ -197,7 +197,7 @@ public abstract class MetricsDynamicMBeanBase implements DynamicMBean {
   public Object invoke(String actionName, Object[] parms, String[] signature)
       throws MBeanException, ReflectionException {
     
-    if (actionName == null || actionName.equals("")) 
+    if (actionName == null || actionName.isEmpty()) 
       throw new IllegalArgumentException();
     
     

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/record/CsvRecordInput.java

@@ -144,7 +144,7 @@ public class CsvRecordInput implements RecordInput {
     
   @Override
   public void startRecord(String tag) throws IOException {
-    if (tag != null && !"".equals(tag)) {
+    if (tag != null && !tag.isEmpty()) {
       char c1 = (char) stream.read();
       char c2 = (char) stream.read();
       if (c1 != 's' || c2 != '{') {
@@ -156,7 +156,7 @@ public class CsvRecordInput implements RecordInput {
   @Override
   public void endRecord(String tag) throws IOException {
     char c = (char) stream.read();
-    if (tag == null || "".equals(tag)) {
+    if (tag == null || tag.isEmpty()) {
       if (c != '\n' && c != '\r') {
         throw new IOException("Error deserializing record.");
       } else {

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/record/CsvRecordOutput.java

@@ -115,7 +115,7 @@ public class CsvRecordOutput implements RecordOutput {
     
   @Override
   public void startRecord(Record r, String tag) throws IOException {
-    if (tag != null && !"".equals(tag)) {
+    if (tag != null && ! tag.isEmpty()) {
       printCommaUnlessFirst();
       stream.print("s{");
       isFirst = true;
@@ -124,7 +124,7 @@ public class CsvRecordOutput implements RecordOutput {
     
   @Override
   public void endRecord(Record r, String tag) throws IOException {
-    if (tag == null || "".equals(tag)) {
+    if (tag == null || tag.isEmpty()) {
       stream.print("\n");
       isFirst = true;
     } else {

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/SecurityUtil.java

@@ -212,7 +212,7 @@ public class SecurityUtil {
   private static String replacePattern(String[] components, String hostname)
       throws IOException {
     String fqdn = hostname;
-    if (fqdn == null || fqdn.equals("") || fqdn.equals("0.0.0.0")) {
+    if (fqdn == null || fqdn.isEmpty() || fqdn.equals("0.0.0.0")) {
       fqdn = getLocalHostName();
     }
     return components[0] + "/" + fqdn.toLowerCase() + "@" + components[2];

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/UserGroupInformation.java

@@ -992,7 +992,7 @@ public class UserGroupInformation {
   @InterfaceAudience.Public
   @InterfaceStability.Evolving
   public static UserGroupInformation createRemoteUser(String user) {
-    if (user == null || "".equals(user)) {
+    if (user == null || user.isEmpty()) {
       throw new IllegalArgumentException("Null user");
     }
     Subject subject = new Subject();
@@ -1027,7 +1027,7 @@ public class UserGroupInformation {
   @InterfaceStability.Evolving
   public static UserGroupInformation createProxyUser(String user,
       UserGroupInformation realUser) {
-    if (user == null || "".equals(user)) {
+    if (user == null || user.isEmpty()) {
       throw new IllegalArgumentException("Null user");
     }
     if (realUser == null) {

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/authorize/ServiceAuthorizationManager.java

@@ -88,7 +88,7 @@ public class ServiceAuthorizationManager {
     String clientPrincipal = null; 
     if (krbInfo != null) {
       String clientKey = krbInfo.clientPrincipal();
-      if (clientKey != null && !clientKey.equals("")) {
+      if (clientKey != null && !clientKey.isEmpty()) {
         try {
           clientPrincipal = SecurityUtil.getServerPrincipal(
               conf.get(clientKey), addr);

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/token/delegation/AbstractDelegationTokenIdentifier.java

@@ -87,12 +87,12 @@ extends TokenIdentifier {
    */
   @Override
   public UserGroupInformation getUser() {
-    if ( (owner == null) || ("".equals(owner.toString()))) {
+    if ( (owner == null) || (owner.toString().isEmpty())) {
       return null;
     }
     final UserGroupInformation realUgi;
     final UserGroupInformation ugi;
-    if ((realUser == null) || ("".equals(realUser.toString()))
+    if ((realUser == null) || (realUser.toString().isEmpty())
         || realUser.equals(owner)) {
       ugi = realUgi = UserGroupInformation.createRemoteUser(owner.toString());
     } else {

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/token/delegation/AbstractDelegationTokenSecretManager.java

@@ -265,7 +265,7 @@ extends AbstractDelegationTokenIdentifier>
       throw new InvalidToken("User " + renewer + 
                              " tried to renew an expired token");
     }
-    if ((id.getRenewer() == null) || ("".equals(id.getRenewer().toString()))) {
+    if ((id.getRenewer() == null) || (id.getRenewer().toString().isEmpty())) {
       throw new AccessControlException("User " + renewer + 
                                        " tried to renew a token without " +
                                        "a renewer");
@@ -321,7 +321,7 @@ extends AbstractDelegationTokenIdentifier>
     HadoopKerberosName cancelerKrbName = new HadoopKerberosName(canceller);
     String cancelerShortName = cancelerKrbName.getShortName();
     if (!canceller.equals(owner)
-        && (renewer == null || "".equals(renewer.toString()) || !cancelerShortName
+        && (renewer == null || renewer.toString().isEmpty() || !cancelerShortName
             .equals(renewer.toString()))) {
       throw new AccessControlException(canceller
           + " is not authorized to cancel the token");

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/HostsFileReader.java

@@ -63,7 +63,7 @@ public class HostsFileReader {
               // Everything from now on is a comment
               break;
             }
-            if (!nodes[i].equals("")) {
+            if (!nodes[i].isEmpty()) {
               LOG.info("Adding " + nodes[i] + " to the list of hosts from " + filename);
               set.add(nodes[i]);  // might need to add canonical name
             }
@@ -80,13 +80,13 @@ public class HostsFileReader {
 
   public synchronized void refresh() throws IOException {
     LOG.info("Refreshing hosts (include/exclude) list");
-    if (!includesFile.equals("")) {
+    if (!includesFile.isEmpty()) {
       Set<String> newIncludes = new HashSet<String>();
       readFileToSet(includesFile, newIncludes);
       // switch the new hosts that are to be included
       includes = newIncludes;
     }
-    if (!excludesFile.equals("")) {
+    if (!excludesFile.isEmpty()) {
       Set<String> newExcludes = new HashSet<String>();
       readFileToSet(excludesFile, newExcludes);
       // switch the excluded hosts

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/StringUtils.java

@@ -348,7 +348,7 @@ public class StringUtils {
    * @return an array of <code>String</code> values
    */
   public static String[] getTrimmedStrings(String str){
-    if (null == str || "".equals(str.trim())) {
+    if (null == str || str.trim().isEmpty()) {
       return emptyStringArray;
     }
 
@@ -408,7 +408,7 @@ public class StringUtils {
       String str, char separator) {
     // String.split returns a single empty result for splitting the empty
     // string.
-    if ("".equals(str)) {
+    if (str.isEmpty()) {
       return new String[]{""};
     }
     ArrayList<String> strList = new ArrayList<String>();

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/nativeio/TestNativeIO.java

@@ -67,7 +67,7 @@ public class TestNativeIO {
 
     assertEquals(System.getProperty("user.name"), stat.getOwner());
     assertNotNull(stat.getGroup());
-    assertTrue(!"".equals(stat.getGroup()));
+    assertTrue(!stat.getGroup().isEmpty());
     assertEquals("Stat mode field should indicate a regular file",
       NativeIO.Stat.S_IFREG, stat.getMode() & NativeIO.Stat.S_IFMT);
   }
@@ -96,7 +96,7 @@ public class TestNativeIO {
               NativeIO.Stat stat = NativeIO.fstat(fos.getFD());
               assertEquals(System.getProperty("user.name"), stat.getOwner());
               assertNotNull(stat.getGroup());
-              assertTrue(!"".equals(stat.getGroup()));
+              assertTrue(!stat.getGroup().isEmpty());
               assertEquals("Stat mode field should indicate a regular file",
                 NativeIO.Stat.S_IFREG, stat.getMode() & NativeIO.Stat.S_IFMT);
             } catch (Throwable t) {

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/ipc/TestSaslRPC.java

@@ -112,7 +112,7 @@ public class TestSaslRPC {
     }
     @Override
     public UserGroupInformation getUser() {
-      if ("".equals(realUser.toString())) {
+      if (realUser.toString().isEmpty()) {
         return UserGroupInformation.createRemoteUser(tokenid.toString());
       } else {
         UserGroupInformation realUgi = UserGroupInformation

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/util/TestStringUtils.java

@@ -231,7 +231,8 @@ public class TestStringUtils extends UnitTestcaseTimeLimit {
     assertArrayEquals(expectedArray, StringUtils.getTrimmedStrings(pathologicalDirList2));
     
     assertArrayEquals(emptyArray, StringUtils.getTrimmedStrings(emptyList1));
-    assertArrayEquals(emptyArray, StringUtils.getTrimmedStrings(emptyList2));
+    String[] estring = StringUtils.getTrimmedStrings(emptyList2);
+    assertArrayEquals(emptyArray, estring);
   } 
 
   @Test